#include<iostream>
#include<vector>
using namespace std;

class Solution {
public:
    int missingNumber(vector<int>& nums) {
        int ret = 0;
        for (auto x : nums)
        {
            ret ^= x;
        }
        for (int i = 0; i <= nums.size(); i++)
        {
            ret ^= i;
        }
        return ret;
    }
};

int main()
{
    return 0;
}